This invention relates to an information transmission system by collaborative filtering wherein a user can send or exchange content data, a program or the like to or with a communication opposite party who has likes and tastes similar to that of the user through a network, and more particularly to a technique for use with an information transmission system of the type described for making it possible for different persons to exchange information in which the persons are much interested with each other through communication between the persons without presupposing the presence of a server which stores a large amount of data and executes a large amount of calculation.
Collaborative filtering is known as a technique which is utilized where users having similar likings or preferences perform information exchange or the like with each other through a network. One of collaborative filtering systems is disclosed, for example, in Japanese Patent Laid-Open No. Hei 9-265478 (hereinafter referred to as Patent Document 1). According to the collaborative filtering, for example, profile information of individual users is compared to calculate a correlativity therebetween to search for a user (cooperation opposite party) having a comparatively high correlativity. Various systems which use this technique have been proposed. However, most of the systems adopt a form of a network centering on a network server (the form is called client-server model and hereinafter referred to simply as “C/S model”). The reason is that the collaborative filtering technique requires a large amount of data and a large amount of calculation.
Meanwhile, in a system wherein contents of music or images are recommended to a user as is disclosed, for example, in Japanese Patent Laid-Open No. 2003-173350 (hereinafter referred to as Patent Document 2), if a user sends a viewing history in the past through the Internet, then contents are recommended from the server to a client machine of the user. Also the system basically uses a form of the C/S model and essentially requires a large-scale server.
A system of another form of a network wherein a population is formed through interpersonal communication (the form is called Peer to Peer network model and hereinafter referred to as “P2P model”) does not require a centralized management mechanism configured using a server machine. Therefore, a system of the P2P model is advantageous in terms of the operation cost. As one of systems of the type described, for example, a system is known wherein profile information of a user is produced based on terminal use history information and stored into a memory card or a like storage and specialized information is provided to the user. A system of the type described is disclosed, for example, in Japanese Patent Laid-Open No. 2001-14324 (hereinafter referred to as Patent Document 3).
As a technique which is utilized by a user to selectively communicate only with a person who owns information useful to the user from among a large number of persons through a network, user profiling is available, and a system which utilizes an individual profile in which profile data obtained by quantifying the individual likes and tastes are registered is known and disclosed, for example, in Japanese Patent Laid-Open No. 2000-76304 (hereinafter referred to as Patent Document 4). According to the system, for example, a certain user extracts a text from information communicated with another user and performs word division or frequency calculation to produce a profile of the user itself. Further, interpersonal communication is performed to produce a profile wherein the appearance frequency degree is evaluated appropriately through comparison with a group which includes the user.